<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>HTML5 History API</title>
    <link rel="stylesheet" href="./common.css">
</head>
<body>
    <!-- url 
    domain , 组织文件,  向用户提供很多资源
    链接把资源组织起来 
    一切皆资源  Restful  -->
    <div class="wrapper">
        <ul class="nav">
            <li><a href="index.html">Home</a></li>
            <li><a href="fluffy.html">Fluffy</a></li>
            <li><a href="socks.html">Socks</a></li>
            <li><a href="whiskers.html">Whiskers</a></li>
        </ul>
        <p class="content">Welcome to Kittens! Home of Fluffy, Socks, and Whiskers. If you're not suffering from a cute overdose within the hour, then you really are a heartless bugger! Now lets look at some cats!
        </p>
        <div class="media">
            <img src="http://www.ichong123.com/uploads/2014/08/m1.jpg" alt="" class="photo">
        </div>
    </div>
    <script>
    // 传统ｗｅｂ网站　发起优化　
    // ａｊａｘ　 刷新整个页面 不用白一下 
    function getHtml(href, callback) {
        // fetch 小弟
        const xhr = new XMLHttpRequest(); // web 2.0   url
        console.log(xhr.readyState);  
        xhr.open("GET", href);
        console.log(xhr.readyState);
        xhr.send() // 发送请求
        console.log(xhr.readyState);
        xhr.onreadystatechange = function() {
            // console.log(xhr.readyState, '-------------');
            if (xhr.readyState == 4) { // 服务器响应 完全到达了
                callback(xhr.responseText);
            }
        }
    }

    function createState(data) {
        // . 可以匹配任何字符 
        // + 匹配一次或多次
        // () 分组 , 
        const contentMatches = data.match(/content">(.+)</);
        // console.log(contentMatches);
        const content = contentMatches[1];
        const photoMatches = data.match(/img.+src="(.+)"\s/);
        const photo = photoMatches[1];
        // console.log(photo);
        return {
            content,
            photo
        }
    }

    // 生命周期  所有的资源都加载完成
    window.addEventListener('DOMContentLoaded', function() {
        // html+css 页面渲染
        // 比load  更早的 js运行, 交互
        // console.log('loaded')
        const links = document.querySelectorAll('.nav li a');
        links.forEach(link => {
            link.addEventListener('click', function(event) {
                // 传统a  点完就白屏 
                event.preventDefault();
                let href = event.target.href;
                // 通用  
                getHtml(href, function(data) {
                    // callback
                    // console.log(data);
                    // 正则的过程 
                    // 新状态 pic  content  
                    let state = createState(data);
                    // console.log(state)
                    document.querySelector('.content').innerText = state.content;
                    document.querySelector('.photo').src = state.photo;
                })
                // const xhr = new XMLHttpRequest();

                // let href = event.
                // console.log(event)
                // console.log(href);
            });
        })
    })

    // window.addEventListener('load', function() {
    //     console.log('onload');
    // })
    </script>
</body>
</html>